There's a hidden world underneath many American communities - abandoned subway lines, sealed up basements, evacuation tunnels.
Below the downtown business district of Oregon's capital city, Salem, is evidence of a long-lost Chinatown.
The path to this historic underworld begins in the basement of the tallest office building in Salem.
Local historian John Ritter appproached the building's owner about exploring the area. He believed there were some long-forgotten chambers and passageways branching off from the basement, and wanted to have a look around.
As Ritter explored the basement, a sagging bookcase caught his eye. When he and Rebecca Maitland, works for the building's owner, moved it aside, they found a doorway leading to a room that no one had set foot in for years.
It was dank and dark. Looking up, they noticed a trap-door in the ceiling. It opened up to the sidewalk above. They figured it served as a place for local merchants to drop gold that would be stored in the vault of the bank that used to operate here.
"I swear there's still, if you get really close, gold speckles on the floor here," says Maitland.
For a historian like Ritter, the find was interesting. But despite the traces of gold, he says this chamber isn't the mother lode.
"I'm on a quest with Rebecca to find Salem's opium dens," he says. It isn't that Ritter enjoys the smell of opium, which he says could still be lingering after more than 130 years. He says the dens would be the only remaining tangible evidence of a once-thriving Chinatown.
Oregon's capital - like many cities in the American west - was once home to hundreds of Chinese immigrants to came to work on the railroad. But anti-Chinese sentiment in the 1880s literally drove some of them underground - where they set up gambling, bootlegging and opium dens.
Whether it's opium dens or gold repositories, the underground history of Salem is a story Ritter wants to tell.
"It would be exciting to see that and validate Salem's underground history, to say yep, here's where it happened, here's what we're finding."
Ritter and fellow explorers have discovered an antique bank vault, an old grocery front, rusting elevators and empty shafts where people once lived.
At one time, secret passageways made it possible to go from building to building without being seen. That was handy if you were the type who patronized speakeasies, drank bootleg liquor and smoked opium.
The discoveries have drawn widespread interest. A recent one-time only tour of some of Salem's underground areas had room for 100 people. More than 300 showed up. Ritter plans to continue his subterranean explorations. And now the retired history professor has a partner. Maitland has become so interested that she's taken up the cause, too.
"I kind of talk about Rebecca and myself as an Indiana Jones pair, except we don't have a whip or a gun," says Ritter, "but I do use a cane a lot."
At least one of their discoveries isn't something from long ago. The two recently stumbled upon a 1970s-era discothèque. But instead of platform shoes, the dance floor was covered with pigeon feathers.